Step-by-step motor



Oct. 14, 1947. VAN 5, mm 2,428,882

STEP-BY-STEP MOTOR Filed June 27, 1945 2 Sheets-Sheet 1 Oct. 14, 1947- VAN s, KOLFF 2,428,882

' STEP-BY-STEP MOTOR 2 Sheets-Sheet 2 Filed June 27, 1945 Patented Oct. 14, 1947 UNITED STATES PATENT OFFICE 2,428,882 STEP-BY-STEP MOTOR Petr-us van Santen Kolff, asslgnor to The Electric Pa., a corporation of Delation, Philadelphia, ware Application June 27,

9 Claims.

1 This invention relates to step-by-step motors, and more particularly to a motor of this type useful for tachometric and like purposes, and

having an extremely. simple and reliable con- I and in which a single electrical impulse serves to advance the armature one step.

Another object is t pro ide a direct current motor which is com act, powerful and constructed of durable parts, and which provides a very fast and positive step-by-step motion useful in a wide variety of applications.

A further object is to provide, in such a motor, devices by which electric energy is used to impart initial motion to the armature and at the same time to store potential energy in a mechanical driving device, and the stored mechanical energy is used to impart further motion tothe armature to complete the operating cycle.

Still further objects and advantages of the invention will be in part apparent and in part pointed out in the following description of a preferred embodiment thereof, as shown in the accompanying drawing, wherein:

Fig. 1 is a vertical transverse sectional view of a step-by-step motor shown geared to a register for use in counting;

Fig. 2 is a partial right side view of the armature of the motor shown in Fig. 1;

Fig. 3 is a view taken along the plane of the line 3-3 of Fig. 2, showing one of the polar projections of the armature in end view;

Fig. 4 is a diagrammatic right side view of the armature, cam and cooperating parts in rest position at the end of the cyclic operation of the motor; some of the parts being shown in disproportionate size to facilitate description;

Fig. 5 is a view similar to Fig. 4, but showing the mechanism in an intermediate position in a cyclic stepping operation;

Fig. 61s a circuit diagram of the motor operatively connected to a source of electriclenergy; and

- Fig. 7 is a diagrammatic view, similar to Fig. 4, showing the cam reversed for clockwise rotation.

Referring particularly to Figs. 1, 2 and 3, the

Harwlch Port, Mara, Tachometer Corpora- 1945, Serial No. 601,897

U-shaped frame of the motor is of iron and includes a base i that may in any manner, and sid sets of axially alined pole 5 or rivets 4. A soft iron extensions or teeth 8 is secured to a shaft be secured to a support e bars 2 in which two s 3 are mounted by pins armature 5 with radial I that is journalled in bearings 8, 9 mounted in the side bars 2 of the motor frame, the axis of the shaft 1 being parallel to and equally spaced from.the

l axes of the alined pairs of stator poles 3. The

armature teeth 6 are of rectangular form, as viewed axially of the shaft, and the ends of the les 3 are preferably of the same form. It is 1 convenient to use round trailing edges of the 3 and to mill off the free e shape, as indicated by the sh ding l teeth 3 may bar stock for the poles ds to the desired 1( Fig. 1. The be rounded off as shown in Fig. 3 when the motor is to operate in only one direction, but the leading and,

same form when the trailing edges of the teeth are preferably of the parts are designed for re- 3 arrangement to permit rotation in either direction.

Field coils iii are arranged on the several poles the armature 5 will be 3 and, as will be explained more fully hereinafter,

advanced by one step,

corresponding to the angular spacing of the armature teeth, by each coils. There are ten our rent pulse to the field armature teeth in the illustrated recorder embodiment that includes a revolutions counter H operated from the shaft I through gears H, A different number course be employed the gear ratio.

A-cam M is secured to I3 having a one-to-one ratio. of armature teeth may of by an appropriate change in the left-hand end of the shaft I by a pin l5, and a pair of followers it are mounted in diametrically opposed housings cam surface by springs are preferably steel ll and yieldingly pressed against the peripheral I8. The followers l8 balls but followers of other shapes may be employed. The cam ll has the same number of teeth or projections as the armature 5, but neither the depressions Hd between adjacent cam projections nor the tips Hit of the cam projections are symmetrically disposed with respect to the armature teeth. Furthermore, the

low points lid are not midway between adjacent tionships result in a tips Hit, and these several unsymmetrical relastep-by-step rotation of the armature 5 and shaft 1 by current pulses transmitted simultaneously to the four field coils l0.

.As shown diagrammatically in ,Fig. 4, the follow rs o balls. it are a e ssed towards each other by their backing springs 18 and they therefore tend to hold the cam H at rest with two of the cam low points I id in the plane D-D that passes through the balls 16, the poles 3 and the shaft 1. The motor is symmetrical about a horizontal of the upper pair of poles 3, and will therefore move the trailing cam tip ll beyond the reference plane D-D, see Fig. 5. Potential energy is thereby stored in the springs l8 and is released, upon the interruption of the current through coils E0, to effect the further rotation of the cam N that restores the parts to the relative positions shown in Fig. 4.

The angular pitch p is 36 in the case of ten armature teeth, and the trailing tooth 6 may be about 16 from the plane DD in the rest position of the motor. The eifective differential magnitude of the current pulses, the magnitude of the load carried by the motor, the strength of the springs I 8.

The circuit connections to the motor are 01 a simple two-wire type, see Fig. 6, with the several field coils in in series with each other and with a source of current I 9 and switch 20. The switch 20 may be actuated by a projection or eccentric 2| on a shaft S when the motor is to actuate a counter for registering the number of revolutions of the shaft S.

The apparatus as shown in Figs. 4 and 5 is designed for counterclockwise rotation but it will be apparent that the direction of rotation may be larly with respect to the armature 5 during this operation to shift the rest position of the armature 5 clockwise by about 10, see Fig. 7. The proper angular setting of the cam is obtained by was previously the trailing tooth and relatively close to the pole 3 is thus advanced so far that the adjacent tooth 6" at the left will be attracted to the pole 3 upon the next pulse excitation of the coils ID.

store mechanical energy for the completion of a one-step advance. When relatively light power is required to carry the load, two of the field coils Ill may be omitted.

It is therefore to be understood that the invention is not limited to the embodiment herein changes in the general arrangement and in the particular constructions and arrangements of the several parts of the step-by-step motor fall within the spirit of the invention as set forth in the following claims.

I claim:

de-energization of the same.

2. In a step-by-step motor, the invention as recited in claim 1 wherein said mechanically stressed means includes means for positively limiting the advance of said armature to a single step for each energization of said electromagnet.

3. In a step-by-step motor, the invention as recited in claim 1, wherein said electromagnet includes a pair of spaced pole pieces at opposite sides of the path of the polar extensions of the armature.

4. In a step-by-step motor, the invention as recited in claim 1, wherein said electromagnet includes a pair of pole pieces at opposite sides of the axis of rotation of said armature.

5. A step-by-step motor, characterized by twostage cyclic operation, comprising a rotatably mounted armature having a plurality of circularly disposed and equally spaced polar projections; an electromagnet fixedly mounted adjacent electromagnet, whereby to complete the second state of cyclic operation.

6. A step-by-step motor, characterized by twostage cyclic operation, comprising a rotatable shaft; an armature mounted on said shaft; a

ed on said shaft, said cam having a continuous serrate track, including a number of teeth equal to the number of said polar projections; and a resiliently biased follower riding on said track, said cam being so positioned angularly with respect to said armature that the follower will normally have a stable position on the track between adjacent teeth and one of said polar pro- J'ections will stand in a position to be attracted to said electromagnet when the latter is energized, and that when the electromagnet is energized and attracts a polar projection the cam is rotated to a position where the follower rests upon an inclined part of the track, whereby, as the second stage of cyclic operation, said follower .will rotate the cam to assume its normal position at which the next successive polar projection is in posi-' tion to be attracted towards said electromagnet upon re-energization of the latter.

'7. A step-by-step motor, characterized by twostage cyclic operation, comprising a rotatable shaft; an armature mounted on said shaft and having a plurality of circularly disposed, equally spaced polar projections; an electromagnet fixedly mounted adjacent to the circular path of said polar projections, whereby, as the first stage of cyclic operation, energization of the electromagnet will attract one of said polar projections to a position of proximity with respect to said electromagnet; a cam inounted on said shaft, said cam having a continuous serrate track including circularly disposed equally spaced teeth equal in number to the number of said polar projections; and a follower, including a spherical element and a spring biasing said element into engagement with said track, said electromagnet, armature,

being so angularly related that earn nd follower W113; said spherical element is seated in stable po tion between two adjacent cam teeth, one ryolar projection of said armature is in position same; movable with the same number as the polar projections of said armature, and a spring-pressed follower bearing on said cam to rotate the same and said armature on de-energization of said electromagnetic means, the depressions of the cam being non-symmetrical with respect to the points of the cam and the points of the cam being non-symmetrical with respect to the polar projections of the armature.

9. A step-by-step motor as recited in claim 8, in combination with means for effectively reversing angular asymmetry of said cam with respect to said polar projections to determine the 30 direction of rotation of said motor.

PETRUS VAN SANTEN KOLFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

